I do not know if you could ever get an reliable answer to that question. November in the BVI was more than 7 inches of rain with 4 inches falling already in December. That is the norm with October, November, and December being wet months. By February it should be dry again and then the cycle will repeat itself. Anytime there are puddles of any kind of fresh water. Adult mosquitos will lay eggs. If the fresh water puddle stays wet until the juvenile mosquitos hatch and evolve into flying inspect larger numbers of each brood survive. That is how the population of mosquitos explode. It has been wet everywhere and there will be mosquitos everywhere. Wind is your only friend coupled with the proper applications of repellent. You need something with at least 20 percent DEET or Picaridin and a lot of it. Almost all of us apply insect repellent inadequately. The primary carrier of Zika is an indoor short distance mosquito. You are at risk there as soon as you get off a plane in Puerto Rico or STT. If you want good protection from mosquito born illness or even just the bites. Get a proper DEET or Picaridin product and put the stuff on correctly before you leave home. Keep applying the stuff 24/7 while you are in the area. Make sure you have the DEET or Picaridin properly applied before you go near the airport, shopping, or any activity ashore. Anywhere near other people across the tropics we are all at risk of ZIKA and the other mosquito born illnesses. The research shows none of the "natural" products are effective. If you get the proper products they research shows DEET and Picaridin are both effective for 7.5 to 8 hours. We now treat insect repellent like sunscreen. We buy the correct stuff and apply the Picaridin or DEET early and often 24/7. Put is on when you get up, reapply after each time you get wet, and apply insect repellent heavily just before you go to sleep. If the bugs are biting you or your crew. You either have the incorrect product or improper application.